xref: /openbmc/linux/mm/memory_hotplug.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
1 /*
2  *  linux/mm/memory_hotplug.c
3  *
4  *  Copyright (C)
5  */
6 
7 #include <linux/stddef.h>
8 #include <linux/mm.h>
9 #include <linux/swap.h>
10 #include <linux/interrupt.h>
11 #include <linux/pagemap.h>
12 #include <linux/bootmem.h>
13 #include <linux/compiler.h>
14 #include <linux/module.h>
15 #include <linux/pagevec.h>
16 #include <linux/writeback.h>
17 #include <linux/slab.h>
18 #include <linux/sysctl.h>
19 #include <linux/cpu.h>
20 #include <linux/memory.h>
21 #include <linux/memory_hotplug.h>
22 #include <linux/highmem.h>
23 #include <linux/vmalloc.h>
24 #include <linux/ioport.h>
25 #include <linux/delay.h>
26 #include <linux/migrate.h>
27 #include <linux/page-isolation.h>
28 #include <linux/pfn.h>
29 #include <linux/suspend.h>
30 #include <linux/mm_inline.h>
31 
32 #include <asm/tlbflush.h>
33 
34 #include "internal.h"
35 
36 /* add this memory to iomem resource */
37 static struct resource *register_memory_resource(u64 start, u64 size)
38 {
39 	struct resource *res;
40 	res = kzalloc(sizeof(struct resource), GFP_KERNEL);
41 	BUG_ON(!res);
42 
43 	res->name = "System RAM";
44 	res->start = start;
45 	res->end = start + size - 1;
46 	res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
47 	if (request_resource(&iomem_resource, res) < 0) {
48 		printk("System RAM resource %llx - %llx cannot be added\n",
49 		(unsigned long long)res->start, (unsigned long long)res->end);
50 		kfree(res);
51 		res = NULL;
52 	}
53 	return res;
54 }
55 
56 static void release_memory_resource(struct resource *res)
57 {
58 	if (!res)
59 		return;
60 	release_resource(res);
61 	kfree(res);
62 	return;
63 }
64 
65 #ifdef CONFIG_MEMORY_HOTPLUG_SPARSE
66 #ifndef CONFIG_SPARSEMEM_VMEMMAP
67 static void get_page_bootmem(unsigned long info,  struct page *page, int type)
68 {
69 	atomic_set(&page->_mapcount, type);
70 	SetPagePrivate(page);
71 	set_page_private(page, info);
72 	atomic_inc(&page->_count);
73 }
74 
75 /* reference to __meminit __free_pages_bootmem is valid
76  * so use __ref to tell modpost not to generate a warning */
77 void __ref put_page_bootmem(struct page *page)
78 {
79 	int type;
80 
81 	type = atomic_read(&page->_mapcount);
82 	BUG_ON(type >= -1);
83 
84 	if (atomic_dec_return(&page->_count) == 1) {
85 		ClearPagePrivate(page);
86 		set_page_private(page, 0);
87 		reset_page_mapcount(page);
88 		__free_pages_bootmem(page, 0);
89 	}
90 
91 }
92 
93 static void register_page_bootmem_info_section(unsigned long start_pfn)
94 {
95 	unsigned long *usemap, mapsize, section_nr, i;
96 	struct mem_section *ms;
97 	struct page *page, *memmap;
98 
99 	if (!pfn_valid(start_pfn))
100 		return;
101 
102 	section_nr = pfn_to_section_nr(start_pfn);
103 	ms = __nr_to_section(section_nr);
104 
105 	/* Get section's memmap address */
106 	memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr);
107 
108 	/*
109 	 * Get page for the memmap's phys address
110 	 * XXX: need more consideration for sparse_vmemmap...
111 	 */
112 	page = virt_to_page(memmap);
113 	mapsize = sizeof(struct page) * PAGES_PER_SECTION;
114 	mapsize = PAGE_ALIGN(mapsize) >> PAGE_SHIFT;
115 
116 	/* remember memmap's page */
117 	for (i = 0; i < mapsize; i++, page++)
118 		get_page_bootmem(section_nr, page, SECTION_INFO);
119 
120 	usemap = __nr_to_section(section_nr)->pageblock_flags;
121 	page = virt_to_page(usemap);
122 
123 	mapsize = PAGE_ALIGN(usemap_size()) >> PAGE_SHIFT;
124 
125 	for (i = 0; i < mapsize; i++, page++)
126 		get_page_bootmem(section_nr, page, MIX_SECTION_INFO);
127 
128 }
129 
130 void register_page_bootmem_info_node(struct pglist_data *pgdat)
131 {
132 	unsigned long i, pfn, end_pfn, nr_pages;
133 	int node = pgdat->node_id;
134 	struct page *page;
135 	struct zone *zone;
136 
137 	nr_pages = PAGE_ALIGN(sizeof(struct pglist_data)) >> PAGE_SHIFT;
138 	page = virt_to_page(pgdat);
139 
140 	for (i = 0; i < nr_pages; i++, page++)
141 		get_page_bootmem(node, page, NODE_INFO);
142 
143 	zone = &pgdat->node_zones[0];
144 	for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
145 		if (zone->wait_table) {
146 			nr_pages = zone->wait_table_hash_nr_entries
147 				* sizeof(wait_queue_head_t);
148 			nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;
149 			page = virt_to_page(zone->wait_table);
150 
151 			for (i = 0; i < nr_pages; i++, page++)
152 				get_page_bootmem(node, page, NODE_INFO);
153 		}
154 	}
155 
156 	pfn = pgdat->node_start_pfn;
157 	end_pfn = pfn + pgdat->node_spanned_pages;
158 
159 	/* register_section info */
160 	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION)
161 		register_page_bootmem_info_section(pfn);
162 
163 }
164 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
165 
166 static void grow_zone_span(struct zone *zone, unsigned long start_pfn,
167 			   unsigned long end_pfn)
168 {
169 	unsigned long old_zone_end_pfn;
170 
171 	zone_span_writelock(zone);
172 
173 	old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
174 	if (start_pfn < zone->zone_start_pfn)
175 		zone->zone_start_pfn = start_pfn;
176 
177 	zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
178 				zone->zone_start_pfn;
179 
180 	zone_span_writeunlock(zone);
181 }
182 
183 static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,
184 			    unsigned long end_pfn)
185 {
186 	unsigned long old_pgdat_end_pfn =
187 		pgdat->node_start_pfn + pgdat->node_spanned_pages;
188 
189 	if (start_pfn < pgdat->node_start_pfn)
190 		pgdat->node_start_pfn = start_pfn;
191 
192 	pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
193 					pgdat->node_start_pfn;
194 }
195 
196 static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
197 {
198 	struct pglist_data *pgdat = zone->zone_pgdat;
199 	int nr_pages = PAGES_PER_SECTION;
200 	int nid = pgdat->node_id;
201 	int zone_type;
202 	unsigned long flags;
203 
204 	zone_type = zone - pgdat->node_zones;
205 	if (!zone->wait_table) {
206 		int ret;
207 
208 		ret = init_currently_empty_zone(zone, phys_start_pfn,
209 						nr_pages, MEMMAP_HOTPLUG);
210 		if (ret)
211 			return ret;
212 	}
213 	pgdat_resize_lock(zone->zone_pgdat, &flags);
214 	grow_zone_span(zone, phys_start_pfn, phys_start_pfn + nr_pages);
215 	grow_pgdat_span(zone->zone_pgdat, phys_start_pfn,
216 			phys_start_pfn + nr_pages);
217 	pgdat_resize_unlock(zone->zone_pgdat, &flags);
218 	memmap_init_zone(nr_pages, nid, zone_type,
219 			 phys_start_pfn, MEMMAP_HOTPLUG);
220 	return 0;
221 }
222 
223 static int __meminit __add_section(int nid, struct zone *zone,
224 					unsigned long phys_start_pfn)
225 {
226 	int nr_pages = PAGES_PER_SECTION;
227 	int ret;
228 
229 	if (pfn_valid(phys_start_pfn))
230 		return -EEXIST;
231 
232 	ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);
233 
234 	if (ret < 0)
235 		return ret;
236 
237 	ret = __add_zone(zone, phys_start_pfn);
238 
239 	if (ret < 0)
240 		return ret;
241 
242 	return register_new_memory(nid, __pfn_to_section(phys_start_pfn));
243 }
244 
245 #ifdef CONFIG_SPARSEMEM_VMEMMAP
246 static int __remove_section(struct zone *zone, struct mem_section *ms)
247 {
248 	/*
249 	 * XXX: Freeing memmap with vmemmap is not implement yet.
250 	 *      This should be removed later.
251 	 */
252 	return -EBUSY;
253 }
254 #else
255 static int __remove_section(struct zone *zone, struct mem_section *ms)
256 {
257 	unsigned long flags;
258 	struct pglist_data *pgdat = zone->zone_pgdat;
259 	int ret = -EINVAL;
260 
261 	if (!valid_section(ms))
262 		return ret;
263 
264 	ret = unregister_memory_section(ms);
265 	if (ret)
266 		return ret;
267 
268 	pgdat_resize_lock(pgdat, &flags);
269 	sparse_remove_one_section(zone, ms);
270 	pgdat_resize_unlock(pgdat, &flags);
271 	return 0;
272 }
273 #endif
274 
275 /*
276  * Reasonably generic function for adding memory.  It is
277  * expected that archs that support memory hotplug will
278  * call this function after deciding the zone to which to
279  * add the new pages.
280  */
281 int __ref __add_pages(int nid, struct zone *zone, unsigned long phys_start_pfn,
282 			unsigned long nr_pages)
283 {
284 	unsigned long i;
285 	int err = 0;
286 	int start_sec, end_sec;
287 	/* during initialize mem_map, align hot-added range to section */
288 	start_sec = pfn_to_section_nr(phys_start_pfn);
289 	end_sec = pfn_to_section_nr(phys_start_pfn + nr_pages - 1);
290 
291 	for (i = start_sec; i <= end_sec; i++) {
292 		err = __add_section(nid, zone, i << PFN_SECTION_SHIFT);
293 
294 		/*
295 		 * EEXIST is finally dealt with by ioresource collision
296 		 * check. see add_memory() => register_memory_resource()
297 		 * Warning will be printed if there is collision.
298 		 */
299 		if (err && (err != -EEXIST))
300 			break;
301 		err = 0;
302 	}
303 
304 	return err;
305 }
306 EXPORT_SYMBOL_GPL(__add_pages);
307 
308 /**
309  * __remove_pages() - remove sections of pages from a zone
310  * @zone: zone from which pages need to be removed
311  * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
312  * @nr_pages: number of pages to remove (must be multiple of section size)
313  *
314  * Generic helper function to remove section mappings and sysfs entries
315  * for the section of the memory we are removing. Caller needs to make
316  * sure that pages are marked reserved and zones are adjust properly by
317  * calling offline_pages().
318  */
319 int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
320 		 unsigned long nr_pages)
321 {
322 	unsigned long i, ret = 0;
323 	int sections_to_remove;
324 
325 	/*
326 	 * We can only remove entire sections
327 	 */
328 	BUG_ON(phys_start_pfn & ~PAGE_SECTION_MASK);
329 	BUG_ON(nr_pages % PAGES_PER_SECTION);
330 
331 	sections_to_remove = nr_pages / PAGES_PER_SECTION;
332 	for (i = 0; i < sections_to_remove; i++) {
333 		unsigned long pfn = phys_start_pfn + i*PAGES_PER_SECTION;
334 		release_mem_region(pfn << PAGE_SHIFT,
335 				   PAGES_PER_SECTION << PAGE_SHIFT);
336 		ret = __remove_section(zone, __pfn_to_section(pfn));
337 		if (ret)
338 			break;
339 	}
340 	return ret;
341 }
342 EXPORT_SYMBOL_GPL(__remove_pages);
343 
344 void online_page(struct page *page)
345 {
346 	unsigned long pfn = page_to_pfn(page);
347 
348 	totalram_pages++;
349 	if (pfn >= num_physpages)
350 		num_physpages = pfn + 1;
351 
352 #ifdef CONFIG_HIGHMEM
353 	if (PageHighMem(page))
354 		totalhigh_pages++;
355 #endif
356 
357 #ifdef CONFIG_FLATMEM
358 	max_mapnr = max(page_to_pfn(page), max_mapnr);
359 #endif
360 
361 	ClearPageReserved(page);
362 	init_page_count(page);
363 	__free_page(page);
364 }
365 
366 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
367 			void *arg)
368 {
369 	unsigned long i;
370 	unsigned long onlined_pages = *(unsigned long *)arg;
371 	struct page *page;
372 	if (PageReserved(pfn_to_page(start_pfn)))
373 		for (i = 0; i < nr_pages; i++) {
374 			page = pfn_to_page(start_pfn + i);
375 			online_page(page);
376 			onlined_pages++;
377 		}
378 	*(unsigned long *)arg = onlined_pages;
379 	return 0;
380 }
381 
382 
383 int online_pages(unsigned long pfn, unsigned long nr_pages)
384 {
385 	unsigned long onlined_pages = 0;
386 	struct zone *zone;
387 	int need_zonelists_rebuild = 0;
388 	int nid;
389 	int ret;
390 	struct memory_notify arg;
391 
392 	arg.start_pfn = pfn;
393 	arg.nr_pages = nr_pages;
394 	arg.status_change_nid = -1;
395 
396 	nid = page_to_nid(pfn_to_page(pfn));
397 	if (node_present_pages(nid) == 0)
398 		arg.status_change_nid = nid;
399 
400 	ret = memory_notify(MEM_GOING_ONLINE, &arg);
401 	ret = notifier_to_errno(ret);
402 	if (ret) {
403 		memory_notify(MEM_CANCEL_ONLINE, &arg);
404 		return ret;
405 	}
406 	/*
407 	 * This doesn't need a lock to do pfn_to_page().
408 	 * The section can't be removed here because of the
409 	 * memory_block->state_mutex.
410 	 */
411 	zone = page_zone(pfn_to_page(pfn));
412 	/*
413 	 * If this zone is not populated, then it is not in zonelist.
414 	 * This means the page allocator ignores this zone.
415 	 * So, zonelist must be updated after online.
416 	 */
417 	if (!populated_zone(zone))
418 		need_zonelists_rebuild = 1;
419 
420 	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
421 		online_pages_range);
422 	if (ret) {
423 		printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
424 			nr_pages, pfn);
425 		memory_notify(MEM_CANCEL_ONLINE, &arg);
426 		return ret;
427 	}
428 
429 	zone->present_pages += onlined_pages;
430 	zone->zone_pgdat->node_present_pages += onlined_pages;
431 
432 	zone_pcp_update(zone);
433 	setup_per_zone_wmarks();
434 	calculate_zone_inactive_ratio(zone);
435 	if (onlined_pages) {
436 		kswapd_run(zone_to_nid(zone));
437 		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
438 	}
439 
440 	if (need_zonelists_rebuild)
441 		build_all_zonelists();
442 	else
443 		vm_total_pages = nr_free_pagecache_pages();
444 
445 	writeback_set_ratelimit();
446 
447 	if (onlined_pages)
448 		memory_notify(MEM_ONLINE, &arg);
449 
450 	return 0;
451 }
452 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
453 
454 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
455 static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
456 {
457 	struct pglist_data *pgdat;
458 	unsigned long zones_size[MAX_NR_ZONES] = {0};
459 	unsigned long zholes_size[MAX_NR_ZONES] = {0};
460 	unsigned long start_pfn = start >> PAGE_SHIFT;
461 
462 	pgdat = arch_alloc_nodedata(nid);
463 	if (!pgdat)
464 		return NULL;
465 
466 	arch_refresh_nodedata(nid, pgdat);
467 
468 	/* we can use NODE_DATA(nid) from here */
469 
470 	/* init node's zones as empty zones, we don't have any present pages.*/
471 	free_area_init_node(nid, zones_size, start_pfn, zholes_size);
472 
473 	return pgdat;
474 }
475 
476 static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
477 {
478 	arch_refresh_nodedata(nid, NULL);
479 	arch_free_nodedata(pgdat);
480 	return;
481 }
482 
483 
484 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
485 int __ref add_memory(int nid, u64 start, u64 size)
486 {
487 	pg_data_t *pgdat = NULL;
488 	int new_pgdat = 0;
489 	struct resource *res;
490 	int ret;
491 
492 	lock_system_sleep();
493 
494 	res = register_memory_resource(start, size);
495 	ret = -EEXIST;
496 	if (!res)
497 		goto out;
498 
499 	if (!node_online(nid)) {
500 		pgdat = hotadd_new_pgdat(nid, start);
501 		ret = -ENOMEM;
502 		if (!pgdat)
503 			goto out;
504 		new_pgdat = 1;
505 	}
506 
507 	/* call arch's memory hotadd */
508 	ret = arch_add_memory(nid, start, size);
509 
510 	if (ret < 0)
511 		goto error;
512 
513 	/* we online node here. we can't roll back from here. */
514 	node_set_online(nid);
515 
516 	if (new_pgdat) {
517 		ret = register_one_node(nid);
518 		/*
519 		 * If sysfs file of new node can't create, cpu on the node
520 		 * can't be hot-added. There is no rollback way now.
521 		 * So, check by BUG_ON() to catch it reluctantly..
522 		 */
523 		BUG_ON(ret);
524 	}
525 
526 	goto out;
527 
528 error:
529 	/* rollback pgdat allocation and others */
530 	if (new_pgdat)
531 		rollback_node_hotadd(nid, pgdat);
532 	if (res)
533 		release_memory_resource(res);
534 
535 out:
536 	unlock_system_sleep();
537 	return ret;
538 }
539 EXPORT_SYMBOL_GPL(add_memory);
540 
541 #ifdef CONFIG_MEMORY_HOTREMOVE
542 /*
543  * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
544  * set and the size of the free page is given by page_order(). Using this,
545  * the function determines if the pageblock contains only free pages.
546  * Due to buddy contraints, a free page at least the size of a pageblock will
547  * be located at the start of the pageblock
548  */
549 static inline int pageblock_free(struct page *page)
550 {
551 	return PageBuddy(page) && page_order(page) >= pageblock_order;
552 }
553 
554 /* Return the start of the next active pageblock after a given page */
555 static struct page *next_active_pageblock(struct page *page)
556 {
557 	int pageblocks_stride;
558 
559 	/* Ensure the starting page is pageblock-aligned */
560 	BUG_ON(page_to_pfn(page) & (pageblock_nr_pages - 1));
561 
562 	/* Move forward by at least 1 * pageblock_nr_pages */
563 	pageblocks_stride = 1;
564 
565 	/* If the entire pageblock is free, move to the end of free page */
566 	if (pageblock_free(page))
567 		pageblocks_stride += page_order(page) - pageblock_order;
568 
569 	return page + (pageblocks_stride * pageblock_nr_pages);
570 }
571 
572 /* Checks if this range of memory is likely to be hot-removable. */
573 int is_mem_section_removable(unsigned long start_pfn, unsigned long nr_pages)
574 {
575 	int type;
576 	struct page *page = pfn_to_page(start_pfn);
577 	struct page *end_page = page + nr_pages;
578 
579 	/* Check the starting page of each pageblock within the range */
580 	for (; page < end_page; page = next_active_pageblock(page)) {
581 		type = get_pageblock_migratetype(page);
582 
583 		/*
584 		 * A pageblock containing MOVABLE or free pages is considered
585 		 * removable
586 		 */
587 		if (type != MIGRATE_MOVABLE && !pageblock_free(page))
588 			return 0;
589 
590 		/*
591 		 * A pageblock starting with a PageReserved page is not
592 		 * considered removable.
593 		 */
594 		if (PageReserved(page))
595 			return 0;
596 	}
597 
598 	/* All pageblocks in the memory block are likely to be hot-removable */
599 	return 1;
600 }
601 
602 /*
603  * Confirm all pages in a range [start, end) is belongs to the same zone.
604  */
605 static int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
606 {
607 	unsigned long pfn;
608 	struct zone *zone = NULL;
609 	struct page *page;
610 	int i;
611 	for (pfn = start_pfn;
612 	     pfn < end_pfn;
613 	     pfn += MAX_ORDER_NR_PAGES) {
614 		i = 0;
615 		/* This is just a CONFIG_HOLES_IN_ZONE check.*/
616 		while ((i < MAX_ORDER_NR_PAGES) && !pfn_valid_within(pfn + i))
617 			i++;
618 		if (i == MAX_ORDER_NR_PAGES)
619 			continue;
620 		page = pfn_to_page(pfn + i);
621 		if (zone && page_zone(page) != zone)
622 			return 0;
623 		zone = page_zone(page);
624 	}
625 	return 1;
626 }
627 
628 /*
629  * Scanning pfn is much easier than scanning lru list.
630  * Scan pfn from start to end and Find LRU page.
631  */
632 int scan_lru_pages(unsigned long start, unsigned long end)
633 {
634 	unsigned long pfn;
635 	struct page *page;
636 	for (pfn = start; pfn < end; pfn++) {
637 		if (pfn_valid(pfn)) {
638 			page = pfn_to_page(pfn);
639 			if (PageLRU(page))
640 				return pfn;
641 		}
642 	}
643 	return 0;
644 }
645 
646 static struct page *
647 hotremove_migrate_alloc(struct page *page, unsigned long private, int **x)
648 {
649 	/* This should be improooooved!! */
650 	return alloc_page(GFP_HIGHUSER_MOVABLE);
651 }
652 
653 #define NR_OFFLINE_AT_ONCE_PAGES	(256)
654 static int
655 do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
656 {
657 	unsigned long pfn;
658 	struct page *page;
659 	int move_pages = NR_OFFLINE_AT_ONCE_PAGES;
660 	int not_managed = 0;
661 	int ret = 0;
662 	LIST_HEAD(source);
663 
664 	for (pfn = start_pfn; pfn < end_pfn && move_pages > 0; pfn++) {
665 		if (!pfn_valid(pfn))
666 			continue;
667 		page = pfn_to_page(pfn);
668 		if (!page_count(page))
669 			continue;
670 		/*
671 		 * We can skip free pages. And we can only deal with pages on
672 		 * LRU.
673 		 */
674 		ret = isolate_lru_page(page);
675 		if (!ret) { /* Success */
676 			list_add_tail(&page->lru, &source);
677 			move_pages--;
678 			inc_zone_page_state(page, NR_ISOLATED_ANON +
679 					    page_is_file_cache(page));
680 
681 		} else {
682 			/* Becasue we don't have big zone->lock. we should
683 			   check this again here. */
684 			if (page_count(page))
685 				not_managed++;
686 #ifdef CONFIG_DEBUG_VM
687 			printk(KERN_INFO "removing from LRU failed"
688 					 " %lx/%d/%lx\n",
689 				pfn, page_count(page), page->flags);
690 #endif
691 		}
692 	}
693 	ret = -EBUSY;
694 	if (not_managed) {
695 		if (!list_empty(&source))
696 			putback_lru_pages(&source);
697 		goto out;
698 	}
699 	ret = 0;
700 	if (list_empty(&source))
701 		goto out;
702 	/* this function returns # of failed pages */
703 	ret = migrate_pages(&source, hotremove_migrate_alloc, 0, 1);
704 
705 out:
706 	return ret;
707 }
708 
709 /*
710  * remove from free_area[] and mark all as Reserved.
711  */
712 static int
713 offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
714 			void *data)
715 {
716 	__offline_isolated_pages(start, start + nr_pages);
717 	return 0;
718 }
719 
720 static void
721 offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
722 {
723 	walk_system_ram_range(start_pfn, end_pfn - start_pfn, NULL,
724 				offline_isolated_pages_cb);
725 }
726 
727 /*
728  * Check all pages in range, recoreded as memory resource, are isolated.
729  */
730 static int
731 check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
732 			void *data)
733 {
734 	int ret;
735 	long offlined = *(long *)data;
736 	ret = test_pages_isolated(start_pfn, start_pfn + nr_pages);
737 	offlined = nr_pages;
738 	if (!ret)
739 		*(long *)data += offlined;
740 	return ret;
741 }
742 
743 static long
744 check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
745 {
746 	long offlined = 0;
747 	int ret;
748 
749 	ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn, &offlined,
750 			check_pages_isolated_cb);
751 	if (ret < 0)
752 		offlined = (long)ret;
753 	return offlined;
754 }
755 
756 static int offline_pages(unsigned long start_pfn,
757 		  unsigned long end_pfn, unsigned long timeout)
758 {
759 	unsigned long pfn, nr_pages, expire;
760 	long offlined_pages;
761 	int ret, drain, retry_max, node;
762 	struct zone *zone;
763 	struct memory_notify arg;
764 
765 	BUG_ON(start_pfn >= end_pfn);
766 	/* at least, alignment against pageblock is necessary */
767 	if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
768 		return -EINVAL;
769 	if (!IS_ALIGNED(end_pfn, pageblock_nr_pages))
770 		return -EINVAL;
771 	/* This makes hotplug much easier...and readable.
772 	   we assume this for now. .*/
773 	if (!test_pages_in_a_zone(start_pfn, end_pfn))
774 		return -EINVAL;
775 
776 	lock_system_sleep();
777 
778 	zone = page_zone(pfn_to_page(start_pfn));
779 	node = zone_to_nid(zone);
780 	nr_pages = end_pfn - start_pfn;
781 
782 	/* set above range as isolated */
783 	ret = start_isolate_page_range(start_pfn, end_pfn);
784 	if (ret)
785 		goto out;
786 
787 	arg.start_pfn = start_pfn;
788 	arg.nr_pages = nr_pages;
789 	arg.status_change_nid = -1;
790 	if (nr_pages >= node_present_pages(node))
791 		arg.status_change_nid = node;
792 
793 	ret = memory_notify(MEM_GOING_OFFLINE, &arg);
794 	ret = notifier_to_errno(ret);
795 	if (ret)
796 		goto failed_removal;
797 
798 	pfn = start_pfn;
799 	expire = jiffies + timeout;
800 	drain = 0;
801 	retry_max = 5;
802 repeat:
803 	/* start memory hot removal */
804 	ret = -EAGAIN;
805 	if (time_after(jiffies, expire))
806 		goto failed_removal;
807 	ret = -EINTR;
808 	if (signal_pending(current))
809 		goto failed_removal;
810 	ret = 0;
811 	if (drain) {
812 		lru_add_drain_all();
813 		flush_scheduled_work();
814 		cond_resched();
815 		drain_all_pages();
816 	}
817 
818 	pfn = scan_lru_pages(start_pfn, end_pfn);
819 	if (pfn) { /* We have page on LRU */
820 		ret = do_migrate_range(pfn, end_pfn);
821 		if (!ret) {
822 			drain = 1;
823 			goto repeat;
824 		} else {
825 			if (ret < 0)
826 				if (--retry_max == 0)
827 					goto failed_removal;
828 			yield();
829 			drain = 1;
830 			goto repeat;
831 		}
832 	}
833 	/* drain all zone's lru pagevec, this is asyncronous... */
834 	lru_add_drain_all();
835 	flush_scheduled_work();
836 	yield();
837 	/* drain pcp pages , this is synchrouns. */
838 	drain_all_pages();
839 	/* check again */
840 	offlined_pages = check_pages_isolated(start_pfn, end_pfn);
841 	if (offlined_pages < 0) {
842 		ret = -EBUSY;
843 		goto failed_removal;
844 	}
845 	printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
846 	/* Ok, all of our target is islaoted.
847 	   We cannot do rollback at this point. */
848 	offline_isolated_pages(start_pfn, end_pfn);
849 	/* reset pagetype flags and makes migrate type to be MOVABLE */
850 	undo_isolate_page_range(start_pfn, end_pfn);
851 	/* removal success */
852 	zone->present_pages -= offlined_pages;
853 	zone->zone_pgdat->node_present_pages -= offlined_pages;
854 	totalram_pages -= offlined_pages;
855 
856 	setup_per_zone_wmarks();
857 	calculate_zone_inactive_ratio(zone);
858 	if (!node_present_pages(node)) {
859 		node_clear_state(node, N_HIGH_MEMORY);
860 		kswapd_stop(node);
861 	}
862 
863 	vm_total_pages = nr_free_pagecache_pages();
864 	writeback_set_ratelimit();
865 
866 	memory_notify(MEM_OFFLINE, &arg);
867 	unlock_system_sleep();
868 	return 0;
869 
870 failed_removal:
871 	printk(KERN_INFO "memory offlining %lx to %lx failed\n",
872 		start_pfn, end_pfn);
873 	memory_notify(MEM_CANCEL_OFFLINE, &arg);
874 	/* pushback to free area */
875 	undo_isolate_page_range(start_pfn, end_pfn);
876 
877 out:
878 	unlock_system_sleep();
879 	return ret;
880 }
881 
882 int remove_memory(u64 start, u64 size)
883 {
884 	unsigned long start_pfn, end_pfn;
885 
886 	start_pfn = PFN_DOWN(start);
887 	end_pfn = start_pfn + PFN_DOWN(size);
888 	return offline_pages(start_pfn, end_pfn, 120 * HZ);
889 }
890 #else
891 int remove_memory(u64 start, u64 size)
892 {
893 	return -EINVAL;
894 }
895 #endif /* CONFIG_MEMORY_HOTREMOVE */
896 EXPORT_SYMBOL_GPL(remove_memory);
897